Suction flat box cover perforation



United States Patent SUCTION FLAT BOX COVER PERFORATION LloydHornbostel, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis., acorporation of Wisconsin Application June 17, 1957, Serial No. 665,919

2 Claims. (Cl. 162-351) The instant invention relates to suction boxesfor use in paper machines, and more particularly, to an improved suctionbox cover structure for use in paper machines such as Fourdriniermachines or cylinder machines.

In Fourdrinier machines, the suction boxes are used to assist in theremoval of water from a web carried on a travelling wire; and incylinder machines suction boxes are used to assist in the removal ofwater from a web carried on a felt. In any case a permeable forming bandis trained across the suction box top carrying the web thereon andsuction through the suction box top is applied to the underside of thepermeable band to assist in removal of water from the web through suchpermeable band.

Although the instant invention has application in either a cylinder orFourdrinier machine, it will be described primarily in connection with aFourdrinier machine.

In general, the suction box top or cover is an elongated plate havingupper and lower faces and parallel longitudinal forward and rear edgesfor supporting a permeable forming band, such as a felt or wire, movingtransversely across the top of the plate from the forward to the rearedge thereof. In Wadleigh US. Patent No. 2,487,202 it is suggested thatit may be advantageous to provide the suction box cover with suctionpassages therein having substantial inclination from the upper to thelower face in the direction from the forward edge toward the rear edge,or in other terms, substantial inclination from the top to the bottom ofthe cover in the direction of travel of the wire passing thereover.Logical explanations are presented for superior dewatering using suctionpassages such as those described by Wadleigh. For example, it has beensuggested that the incline downward and in the direction of travel ofthe wire permits the suction passages to function as scrapers to removewater from the bottom of the wire and to withdraw water therefrom morereadily because the suction passages are inclined at least to someextent in the direction in which the momentum of the water tends tocarry water adhering to the bottom of the wire.

The instant invention, in contrast, is based upon the discovery thatinclination of the suction passages in exactly the opposite direction(to that proposed by Wadleigh) results in unusually and unexpectedlysuperior water removal. For example, using a suction box cover whereinthe suction passages have substantial inclination from the upper to thelower face in the direction from the rear edge toward the forward edgeor in the direction opposite to the direction of travel of the wire itis found that the rate of water removal, particularly at moderate papermachine speeds, is almost twice the rate of water removal that isobtained under otherwise identical operating conditions except for theinclination of the suction passages downwardly in the direction of wiretravel (as taught by Wadleigh).

It is, therefore, an important object of the instant invention toprovide an improved suction box cover for paper machines.

It is further object of the instant invention to provide an improvedcover for a suction box of a paper machine comprising an elongated platehaving upper and lower faces and parallel longitudinal farward and rearedges for supporting a permeable .forming band moving transverselyacross the top of the plate from the forward to the rear edge thereof,said plate having a plurality of suction passages therein havingsubstantial inclination from the upper to the lower face in thedirection from the rear edge and toward the forward edge.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

On the drawings:

Figure 1 is an essentially diagrammatic elevational view of a papermachine forming section employing a suction box embodying the instantinvention;

Figure 2 is a top plan view of a suction box'embodying the instantinvention;

Figure 3 is an enlarged fragmentary top plan view of a suction box coverembodying the instant invention; and

Figure 4 is an enlarged detail sectional elevational view takensubstantially along the line IV-IV of Figure 2.

As shown on the drawings:

In Figure 1, a paper machine indicated generally by the referencenumeral 10 is shown comprising an endless forming wire 11 trained abouta breast roll 12, a couch roll 13 and lower return rolls 14, 15 and 16.Stock flows from a head box 17 onto the top run of the wire 11 whereatdewatering is initially carried out during the run of the wire 11 overtable rolls 18, 18, etc. After partial dewatering of the web W on thewire 11 passing over the table rolls 1'8, 18; the wire 11 with the web Wthereon pass over a plurality of suction boxes 19, 20 and 21. Thesuction boxes are provided with a perforate cover 19a, 20a, 21a,respectively, which supports the wire 11 from beneath while suction isapplied thereto through the covers 19a,

20a, 21a from within the suction boxes 19, 20 and 21, respectively. Theinstant invention resides in an improved structure for a suction boxcover such as the suction box cover 1% shown in Figure 2.

In Figure 2, a top plan View of the suction box cover 19a is shown andthe suction box cover 19a comprises an elongated plate having an upperface 30 shown in Figure 2 and a lower face 31 (shown only in Figure 4).The cover 19 has parallel longitudinal forward (32) and rear (33) edgesand the permeable forming band or wire 11 moving in Figures 2, 3 and 4in the direction indicated by the arrows moves across the top 30 of thecover 19a from the forward edge 32 to the rear edge 33.

The details of the suction passages are not shown in Figure 2, but theyare shown in Figures 3 and 4. As will be seen from Figures 3 and 4suction passages in the form of holes of circular cross-section 34, 35and 36 are shown in top plan view in Figure 3 and it will be noted thatthey have substantially uniform cross-section throughout their length,but these holes or suction passages 34, 35 and 36 are inclineddownwardly from the top 30 opposite to the direction of travel of thewire 11. In Figure 4, additional suction passages 37, 38, 39 and 40 areshown in a sectional elevational view, so it can be readily appreciatedthatthe holes 37, etc. are inclined substantially from the upper face 30to the lower face 31 in the direction from the rear edge 33 toward theforward edge 32. For the sake of simplicity the views 2, 3 and 4 are notmade strictly to scale. In actual practice a suction box cover has athickness of about 1 to 1% inches and holes drilled therein havediameters within the range of about A to inch. In order to demonstratethe instant invention, a forming wire at a tension of 25 pounds per inchis drawn over a suction box wherein a vacuum of 6 inches is maintainedthereon. A fibrous web is carried on the wire. For the purposes of theinstant demonstration, the fibrous web employed is a felt which issupplied with water at a rate of 10 gallons per minute. The wire withthe moist fibrous web thereon is drawn acrosssuction box covers havingdifierent structures at a speed of 1500 feet per minute. Identicaloperating conditions are used employing a suction box cover having holesdrilled at an incline downwardly in the direction of wire travel andholes drilled at an incline downwardly in the direction opposite to wiretravel. The angle of incline in each case being 45 and the hole sizesbeing inch in diameter, with the same total amount of open area in eachsuction box. It was found that the rate of removal of water (as measuredcoming from the suction box) for the suction box cover wherein the holesare inclined downwardly opposite to the di-' rection of wire travel was4.5 gallons per minute, Whereas the rate of removal of water for thesuction box cover wherein the holes were inclined downwardly in thedirection of'wire travel was 2.4 gallons per minute.

The angle of incline of the holes (from the horizontal plane of the topsurface 30 of the cover) may range from 30 to 75 or 80 but is preferably45 to 60 .It will be understood that modifications and variations may beeifected without departing fromthe spirit and scope a suction boxbeneath same for the removal of water from aweb of paper being" formedon the wire, the improvement which consists of a stationary cover forsaid box, which cover is perforated with suction passages each of whichis of substantially uniform cross-section throughout its length andsubstantially all of which passages have substantial inclination fromtop to bottom of the cover in the 1 direction opposite to the directionof travel of the wire.

2.' In a paper making machine, a cover for a suction box, and apermeable forming band in contact with said cover, said cover comprisingan elongated plate having upper and lower faces and parallellongitudinal forward and rear edges for supporting the permeable formingband moving transversely across the top of the plate from the forward tothe rear edge thereof, said plate having a plurality of suction passagestherein substantially all of which have substantial inclination from theupper to the lower face in the direction from the rear edge and towardthe forward edge in the direction of travel of the forming band movingthereover.

References Cited in the file of this patent UNITED STATES PATENTS

